Erythromycin A (Em) is a medically important antibiotic produced by fermentation of the Actinomycete Saccharopolyspora erythraea (Bunch and McGuire 1953). More recently it has also become increasingly used as the chemical starting point for the generation of a new generation of semi-synthetic macrolide derivatives which has created a demand for the production of larger quantities of this bulk compound. In the past, increasing product output from well-developed fermentation processes involved either increasing the size of the fermentation plant, or using the traditional empirical mutate-and-screen approach to strain improvement (Queener and Lively, 1986). Because commercial scale fermentors are very costly and the traditional strain improvement methods do not reliably result in significantly better strains, a rational approach to strain improvement involving metabolic engineering of antibiotic producing organisms has been developed. The approach involves using genetic engineering to increase the expression of positive regulators of antibiotic production.
To find positive regulators of erythromycin projection from Sac. erythraea a protocol involving a simple visual screen that has been used successfully in the past for the isolation of antibiotic regulatory genes from other Actinomycete species was followed(Horinouchi et al., 1983; Horihouchi and Beppu, 1984). A slightly different method than Horinuchi and et al. (1983) and others since then was used (Romero, et al., 1992; Fernandez-Moreno et al., 1992; Ishizuka et al., 1992) to discover genes from Sac. erythraea that were different from any of those previously found to stimulate antibiotic production in other Actinomycetes (Chater and Bibb, 1997). The present invention describes the cloning and characterization of a DNA fragment carried by pFL37 which contains two genes involved in starch utilization and one new regulatory gene.